As used herein, an “LC circuit” is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. Such circuits are also known as resonant circuits, tank circuits, or tuned circuits. They are referred to as “reactive” circuits because both the inductance and capacitance of an LC circuit have a non-resistive impedance that varies with the frequency of a signal applied to the LC circuit.
LC circuits are can be used for generating signals at a particular frequency or picking out a signal at a particular frequency from a more complex signal. They are key components in many electronic devices, particularly radio equipment and are commonly found in oscillators, filters, tuners and signal mixers. They are also used in electronic ignition systems.
An LC circuit is “resonant” at a frequency at which the inductive and capacitive reactances are of equal magnitude and cancel each other. The resonant frequency of an LC circuit is expressed as ωo=1/√LC where L is and C is the capacitance and farads.
Because inductive and capacitive reactances cancel each other at the LC circuit's resonant frequency, it is often necessary to determine a particular frequency at which an LC circuit is resonant. Determining a resonant frequency, however, can be difficult, however, because actual inductance and actual capacitance will change between device due to variations in how an inductor and a capacitor are constructed. An apparatus and method for accurately determining the resonant frequency of an LC circuit would be an improvement over the prior art.